Apushatayid & misteryudi – no one said that you don’t have to dress tzniusly when there are no men around. I was just explaining why men have a right to be concerned about the situation.
RY – Terrible analogy. It’s not an allergy. An allergy by definition is not the norm. You wouldn’t refer to an inability to handle poison as an allergy. If the Torah has established the fact that normal men are affected by certain things and are not allowed to see them, that is not an allergy. According to the Torah, dressing untzniusly is lifnei iver.
Additionally, most schools don’t allow peanuts on the premises if there is even one student who is allergic.